Section 675IAC15-2-62. Size of vent piping

   (a) Main Vent. The drain piping for each toilet shall be vented by a one and one-half inch (1 1/2") minimum diameter vent connected to the main drain by one of the following methods:

(1) A one and one-half inch (1 1/2") diameter (min.) individual vent pipe or equivalent directly connected to the toilet drain and extended undiminished outside through the roof.

(2) A one and one-half inch (1 1/2") diameter (min.) continuous vent or equivalent indirectly connected to the toilet drain piping through a two inch (2") wet-vented drain that carries the waste of not more than one (1) fixture.

(3) Two (2) or more vented drains when at least one is wet-vented, or two inch (2") diameter (minimum), and each drain is separately connected to the main drain.

  (b) Individual Vents. Unless protected with an anti-siphon trap vent device, each individually vented fixture with a one and one-half inch (1 1/2") or smaller trap shall be provided with a vent pipe equivalent in area to a one and one-fourth inch (1 1/4") nominal pipe size. The main vent, toilet vent and relief vent, and the continuous vent of wet-vented systems shall have an area equivalent to a one and one-half inch (1 1/2") nominal pipe size.

  (c) Common Vent. When two fixture traps located within the distance allowed from their vent have their trap arms connected separately at the same level into an approved double fitting, an individual vent pipe may serve as a common vent without any increase in size.

  (d) Intersecting Vents. Where two (2) or more vent pipes are joined together no increase in size shall be required; however, the largest vent pipe shall extend full size through the roof.

  (e) Distance of fixture trap from vent shall not exceed the values given in Table 2B, below.

  (f) When a combination of two (2) or more water closets, sinks, showers, urinals, or clothes washing equipment are installed the Indiana plumbing code (675 IAC 16-1 [675 IAC 16-1 was repealed filed Sep 22, 1988, 2:35 p.m.: 12 IR 341, eff Jan 2, 1989. See 675 IAC 16-1.2.]) shall apply for mobile system─commercial transitory.

TABLE 2B
Maximum Distance of Fixture Trap from Vent
Size of Fixture Drain (Inches)	Distance Trap to Vent
1 1/4	4 feet 6 inches
1 1/2	5 feet 0 inches
2	5 feet 0 inches
3	6 feet 0 inches

(Fire Prevention and Building Safety Commission; 675 IAC 15-2-62; filed Mar 25, 1986, 1:44 pm: 9 IR 2000, eff Jun 15, 1986; readopted filed Nov 29, 2001, 12:21 p.m.: 25 IR 1306; readopted filed Sep 21, 2007, 9:20 a.m.: 20071010-IR-675070388RFA; readopted filed Oct 10, 2007, 9:16 a.m: 20071031-IR-675070388RFA; readopted filed Aug 4, 2011, 8:35 a.m.: 20110831-IR-675110254RFA)